Circular Face Research Articles

Cradle-to-cradle business model tool: Innovating circular business models for startups

Born circular startups play a pivotal role in implementing high-level circularity to fight resource depletion and address climate change. In developing circular business model innovation, circular startups face the challenge of lacking legitimacy, which can be approached by certifications provided by concepts like Cradle-to-Cradle. As there is currently no supporting tool to develop such business models, this paper employs a design science research approach and proposes a Cradle-to-Cradle (C2C) Business Model Tool. The tool is developed based on a literature review, feedback from 42 users in six demonstration workshops and is finally tested with eight startups. It succeeds in aiding born circular startups in navigating the venturing process with a focus on high-level circularity. In this paper, C2C principles developed for the product level are theoretically linked to the business model level. The tool addresses elements such as partnerships, communication, and action-taking, thereby contributing to the literature on circular business model innovation and serving as a practical resource for born circular startups.

Inclusion or Exclusion?: Gendered Experiences and Strategies of Migrants in Informal Settlements in Bengaluru

Internal migration, nearly four times more than the migration across national boundaries, accounts for the largest human movements in the world. In context of agrarian distress, circular migration between the rural and the urban is a common livelihood trajectory of at least 100 million Indians. It is known that circular migrants face numerous economic and social challenges of survival in the city. This article focuses on gendered experiences and strategies adopted by migrants for inclusion in informal settlements in Bengaluru. Drawing on the concepts of social exclusion, inclusion and agency, we use household surveys ( n = 1,109) in 30 informal settlements in Bengaluru in 2016, semi-structured interviews ( n = 20) in one informal settlement, key informant interviews ( n = 5) and participant observation in events and meetings in the city to illustrate individual and collective strategies used by diverse groups and the ways in which these are gendered. We find that the length of stay in the settlement is a crucial determinant of social inclusion in the city.

Estimation of Diameter at Breast Height in Tropical Forests Based on Terrestrial Laser Scanning and Shape Diameter Function

Estimating forest carbon content typically requires the precise measurement of the trees’ diameter at breast height (DBH), which is crucial for maintaining the health and sustainability of natural forests. Currently, Terrestrial Laser Scanning (TLS) systems are commonly used to acquire forest point cloud data for DBH estimation. However, traditional circular fitting methods face challenges such as a reliance on forest elevation normalization and underfitting of large trees. This study explores a novel approach, the Shape Diameter Function (SDF) algorithm model, leveraging the advantages of three-dimensional point cloud information to replace traditional circular fitting methods. This study employed a parallel approach, combining the Digital Elevation Model (DEM) with Density-Based Spatial Clustering of Applications with Noise (DBSCAN) to segment tree point clouds at breast height. Additionally, a point cloud SDF algorithm based on an octree structure was proposed to accurately estimate individual tree DBH. The research data were obtained from tropical secondary forests located in Cameroon, Peru, Indonesia, and Guyana, with forest ground point cloud data acquired via TLS. The experimental results demonstrated the superior performance of the SDF algorithm in estimating DBH. Compared with the Random Sample Consensus (RANSAC) and Hough transform methods, the Root Mean Square Error (RMSE) decreased by 28.1% and 47.8%, respectively. Particularly in estimating DBH for large trees, the SDF algorithm exhibited smaller errors, indicating a closer alignment between the estimated individual tree DBH values and those obtained from manual measurements. This study presented a more accurate DBH estimation algorithm, contributing to the exploration of improved forest carbon content estimation methods.

Improving Location Decisions For Charity Retailers: Applying Operations Research and Customer Discovery

This study provides a novel methodology at the nexus of Customer Discovery and business analytics for critical location decisions charity retailers with circular supply chains face. It integrates spatial network analysis with Customer Discovery and multicriteria decision-making. Traditional analyses are primarily based on customer location but for donated goods applying Customer Discovery and expert judgment and systematic analysis of data prevails. This integration provides an agile approach to producing optimal alternative locations, which can be applied to Habitat for Humanity ReStore, and Goodwill Industries, and similar organizations globally. This cross-disciplinary approach is practical and cost-effective and can increase efficiency, decrease risks, and strengthen organizational buy-in. It categorizes the drivers affecting location decisions and combines the current business model search techniques and an overall analytical framework to create the Expert Knowledge and Evidence-Based Location Methodology (EKELM).

Comparison of small female PMHS thoracic responses to scaled response corridors in a frontal hub impact

Objective The purpose of this study was to generate biomechanical response corridors of the small female thorax during a frontal hub impact and evaluate scaled corridors that have been used to assess biofidelity of small female anthropomorphic test devices (ATDs) and human body models (HBMs). Methods Three small female postmortem human subjects (PMHS) were tested under identical conditions, in which the thorax was impacted using a 14.0 kg pneumatic impactor at an impact velocity of 4.3 m/s. Impact forces to PMHS thoraces were measured using a load cell installed behind a circular impactor face with a 15.2 cm diameter. Thoracic deflections were quantified using a chestband positioned at mid-sternum. Strain gages installed on the ribs and sternum identified fracture timing. Biomechanical response corridors (force-deflection) were generated and compared to scaled small female thoracic corridors using a traditional scaling method (TSM) and rib response-based scaling method (RRSM). A BioRank System Score (BRSS) was used to quantify differences between the small female PMHS data and both scaled corridors. Results Coefficients of variation from the three small female PMHS responses were less than 2% for peak force and 7% for peak deflection. Overall, the scaled corridor means determined from the TSM and RRSM were less than two standard deviations away from the mean small female PMHS corridors (BRSS < 2.0). The RRSM resulted in smaller deviation (BRSS = 1.1) from the PMHS corridors than the TSM (BRSS = 1.7), suggesting the RRSM is an appropriate scaling method. Conclusions New small female PMHS force-deflection data are provided in this study. Scaled corridors from the TSM, which have been used to optimize current safety tools, were comparable to the small female PMHS corridors. The RRSM, which has the great benefit of using rib structural properties instead of requiring whole PMHS data, resulted in better agreement with the small female PMHS data than the TSM and deserves further investigation to identify scaling factors for other population demographics.

Exploring the Dynamic of a Circular Ecosystem: A Case Study about Drivers and Barriers

The circular economy (CE) aims to minimize the environmental impact caused throughout the entire production chain, which can be achieved by implementing circular strategies in collaboration with different actors within a business ecosystem. Although the close relationship between CE and business ecosystem concepts, which originated the term “circular ecosystem”, research about this subject is necessary, given the scarcity of empirical studies addressing the phenomenon. Therefore, this study aims to contribute by investigating a Brazilian circular ecosystem specialized in the manufacture of ecological tiles through recycled carton packages. The exploratory case study method was selected to characterize the ecosystem and identify 27 drivers and 17 barriers that enhance and hinder the ecosystem’s existence and functioning. Our findings, summarized by a framework, demonstrate the need for integration among the ecosystem’s actors so that its value proposition can be delivered. This issue is crucial for collecting post-consumer packaging for recycling and manufacturing ecological tiles. However, actors within the circular ecosystem face some obstacles to collecting the amount of packaging post-consumer material, such as the COVID-19 pandemic. Finally, this work generates discussions and future studies on circular ecosystems, especially in the Brazilian context, where there is little evidence in this research field.

Three-dimensional stochastic geological modeling for probabilistic stability analysis of a circular tunnel face

This study is devoted to the probabilistic stability analysis of a circular tunnel face incorporating a three-dimensional geological model which is composed of two correlated random fields representing the spatial variability of soil shear strength parameters. The Fast Fourier Transform-Moving Average is adopted for random field generations which takes advantage of discrete Fourier transforms to achieve an easy and time-saving calculation over a large model size. By matching the geological units and failure mechanism elements according to their spatial locations, the employed discretization-based failure mechanism of tunnel face establishes the connection between the stochastic geological model and the mechanical solution model in the framework of limit analysis. By running the Monte Carlo simulation, the failure probability of tunnel face can be obtained for tunnel designs. For the purpose of validation, the proposed method is compared with the numerical approach of FLAC3D by performing deterministic analyses based on the same geological model. Next, parametric analysis is presented to show the influences of autocorrelation length, cross-correlation coefficient, and stratigraphic dip on the failure probability of tunnel face. Finally, a case study considering the failure probability of tunnel face in multilayer soils is discussed to give an example of the practical use of the proposed approach. Conclusively, this method can well simulate the spatial variability of soil properties and the distribution of soil layers; the calculated results can give some guidance for practical tunnel designs.

Stability analysis of a non-circular tunnel face in soils characterized by modified Mohr-Coulomb yield criterion

In many studies, the face stability evaluations of underground excavations have been performed with an equal-area circular tunnel face instead of the real tunnel shape. This equivalent method greatly facilitates the model construction, but sacrifices the calculation accuracy. To solve this issue, a non-circular tunnel is studied here to assess its face stability by kinematical approach where the discretization-based failure mechanism is used to describe the face failure. In the laboratory tests, it is also found that the soil strength in tensile regime is significantly reduced which is much smaller than the one described by the classical Mohr-Coulomb yield criterion. For this purpose, the tensile strength cut-off is introduced to define a linearly varying soil dilatancy angle with the rotation angle when the tensile stress can be expected in soils. On this basis, the failure mechanism has such a feature that the failure surface in tensile regime is accelerated to bend and eventually forms a rounded corner at the top. The proposed approach is compared with the existing methods in literature and the finite difference method of FLAC3D which proves that the proposed approach has sufficient accuracy and great efficiency. Finally, an engineering example of a tunnel in Hunan Province, China is studied using the proposed approach and some suggestions are given for practical tunnel excavations.

The KK principle and rotational symmetry

The KK principle and rotational symmetry

A limit equilibrium model for the reinforced face stability analysis of a shallow tunnel in cohesive-frictional soils

Although a variety of theoretical models have been developed to assess the stability of reinforced tunnel faces, the failure mechanisms in these models are inconsistent with the experimental results. This study establishes a 3D model for the stability analysis of a reinforced tunnel face based on the limit equilibrium method and strength reduction technique. This model considers the horizontal soil arching effect and has a reasonable failure mechanism that is composed of two parts: a truncated elliptical cylinder (upper part) and a wedge bound by a log-spiral-shaped slip surface (lower part). The tension failure of the bolts and shear failure of the grout-soil interface are considered in the calculation of the supporting force of the face bolts. For the sake of verification, the results are compared with those from numerical method and typical limit equilibrium methods. The comparisons show that the results obtained by the proposed model agree well with the numerical simulation results, and the average relative difference and absolute difference are 4.89% and 0.10, respectively.Moreover, when the bolt length is shorter than the optimum length, the safety factor and failure mechanism increase with increasing length; when the bolt length exceeds the optimum length, the safety factor remains constant, while the failure mechanism decreases and then remains unchanged. In addition, the applicability of the proposed model for a circular tunnel face is demonstrated by comparing the results of the proposed model with those of previous studies. At the end of this work, design nomograms are presented to allow the proposed model to be used by engineers.

An accurate method for detecting moving circular face with chamfer in video

A Circle is a common shape in mechanical parts, which projects as ellipse in image or video. In industrial video, target ellipse is often chaotic due to chamfer interference and external interference. An algorithm is proposed to precisely detect ellipse in video on basis of arc analysis in this paper. Compared with the previous methods, the algorithm adds the step of re-extracting the omitted arcs in first detection, and distinguishes target from interference, so it is more accurate. Combined with a video about the fatigue experiment of self-lubricating joint bearing to analyze, the effectiveness and accuracy of this algorithm are verified intuitively.

Failure potential of a circular tunnel face under steady-state unsaturated flow condition

In natural geotechnical structures, especially for those in the vicinity of water bodies or subjected to rainfalls, the soil properties are more likely governed by the unsaturated soil constitutive model rather than the fully saturated or dry one. In this contribution, the theory of unsaturated soil mechanics is introduced to tackle the stability problem of a circular tunnel face under steady-state unsaturated flow condition. By making reference to the existing findings, a generalized analytical solution for the vertical suction stress profile is discussed which permits to deal with unsaturated soil problems with the classical limit analysis method. An extended Mohr-Coulomb yield criterion is presented to characterize the tunnel face failure in unsaturated soil where the effect of suction stress on tunnel face stability is interpreted as the apparent cohesion. The increase in shear strength of unsaturated soil due to the existing of apparent cohesion is considered as a combined effect of n, α, ks and q, which respectively correspond to the pore size parameter, the inverse of air entry value (AEV), the saturated hydraulic conductivity and the flow rate. Within the framework of limit analysis, an advanced three-dimensional (3D) failure mechanism is used to include the unsaturated shear strength parameters into the work rate equation which eventually yields the critical retaining pressure for tunnel face stability. Parametric analysis is performed to show the influence of different unsaturated soil parameters on tunnel face stability. Four representative soil types are investigated to give some suggestions for tunnel excavations and designs in unsaturated soil.

Resistance ceramic-filled annular welding of DP980 high-strength steel

The extensive application of automobile high-strength steel requires high welding strength. A composite ceramic-filled annular electrode is designed based on the concept of controlling heat distribution and changing the nugget-growth mode. DP980 high-strength steel sheets were resistance welded to explore the effect of the annular electrode, and a traditional resistance spot electrode was also used for comparative analysis. The formation and mechanical properties of the nugget were analyzed. The results show that the resistance annular welding formed an annular nugget whose plan view is similar to the end face of the electrode. The annular nugget had a smaller surface indentation depth than the spot-welded nugget. Under the same external diameter of the end face of the electrode, applying the annular electrode produced a nugget area larger than that produced by a traditional circular end face electrode, thereby providing higher tensile and peeling strengths within a larger welding process window. The numerical simulation results of resistance annular welding (RAW) indicated that no current passed in the ceramic filled area; a small annular liquid nugget formed at the initial stage, and then grew inward and outward simultaneously during the welding process.

PRIORITY METERING CONTROL FOR AN URBAN CIRCULAR INTERSECTION

Circular intersections have been used in transportation systems since the 1900s. Threetypes of circular intersections have been used in the United States: traffic circles, rotaries androundabouts. While the use of traffic circles and rotaries in recent decades was found to haveresulted in high crash rates, safety issues have been mitigated for roundabouts through the use ofimproved geometric designs.Nevertheless, all three types of circular intersections face capacity problems duringperiods of high traffic volume, resulting in long queues and delays. Signal metering wasintroduced to reduce long queues and delays on the dominant approaches to circularintersections by stopping the flow of traffic from other approaches. This methodology was foundto ease congestion for circular intersections with historically high traffic volumes. However, mostsignal metering at those intersections employ fixed signal timing, in which the metering rate is notresponsive to changes in traffic condition. This study investigates the performance of an adaptivemetering system for circular intersections. The system was implemented on a real traffic circlehaving high and unbalanced volumes. The model was calibrated, and a case study was simulatedfor peak-hour traffic conditions. Using the PTV VISSIM application programming interface, thealgorithm was tested and the performance of the system was compared to the current intersectionoperation. The results showed that adaptive metering can significantly reduce delays and queuesat a traffic circle. This preliminary study can be a useful reference for the development of prioritycontrolledcircular intersections.

Rotational Failure Mechanism for Face Stability of Circular Shield Tunnels in Frictional Soils

Face stability analyses of shield‐driven tunnels are often carried out to determine the required support pressure on the tunnel face. Although various three‐dimensional mechanisms have been proposed for circular faces of tunnels in frictional and/or cohesive soils to obtain the limit support pressure, the most critical one has not yet been found. Based on a rotational failure mechanism for the frictional soils, this paper modifies the circular cross section as an ellipse to make the generating collapse surface inscribe the entire circular tunnel face. Using the kinematical approach of limit analysis yields an upper bound to the limit support pressure. Through comparisons with the existing results in the literature, the improved mechanism can better estimate the upper bound and is very similar to the observed failures in the experimental tests. The influences of the pore water pressure are also included in the stability analysis of tunnel faces. Calculated upper‐bound solutions are presented in a condensed form of charts for convenient use in practice.

Upper bound solutions for face stability of circular tunnels in non-homogeneous and anisotropic clays

This paper presents a three-dimensional stability analysis of a circular tunnel face in non-homogeneous and anisotropic undrained clay using the kinematic approach (upper bound) of limit analysis. The proposed failure mechanism consists of a cylindrical rigid block and a toroidal shear zone with variable radius, and the closed-form analytical expressions of velocity field are derived within the framework of an orthogonal curvilinear coordinate system. The critical collapse-supporting pressure and stability ratio are obtained through optimization with respect to the geometrical parameters of the mechanism. Two types of non-homogeneous undrained strength, linearly changing with depth, and two-layer clays with constant undrained strength are investigated. Meanwhile, the 3-D finite element analysis is employed to validate the proposed failure mechanism. The upper bound solutions of the stability ratio of the proposed mechanism compare reasonably well with the upper bound solutions from the finite element analysis and show significant improvements over the existing upper bound solutions in single layer clays with homogeneous and isotropic undrained strength. The results show that the critical collapse pressure decreases with the increase in the non-homogeneous ratio and the anisotropic ratio and increases with the ratio between the undrained strength of the top layer and of the bottom layer.

An evaluation of the Effect of Surface Treatment On Amalgam Repair

The purpose of this in vitro study was to evaluate the effect of different surface treatments on shear bond strength of repaired amalgam using two types of amalgam. 120 acrylic blocks (2.7cm diameter by 2.0cm high) were constructed from cold cure resin, each one contained cylindrical hole (7mm diameter by 2mm high) on its circular face that filled with amalgam. The samples were divided into immediate repair group and delayed repair group, which was stored and incubated at 37C0 for one month. After aging the amalgam surface of delayed repair was finished with carbide bur and polished with abrasive rubber cup then divided into three groups according to the surface treatment that include group with out surface treatment, group roughened with diamond bur and the last group was abraded with aluminum oxide (50m) particles size, both immediate and delayed repair were further subdivided according to the type of amalgam used into three subgroups. The repair procedure was done by using a Teflon split mold which containing an opening (3mm diameter by 5mm high) then all the samples were storage and incubated at 37C0 for one week prior to testing.Testing was done by applying shear force at the interface between the initial and repair amalgam with special designed chisel shape rod by using Zwick testing machine at across head speed of 5mm/min.Analysis of the results showed that the shear bond strength in immediate repair were significant higher than of delayed repair and the group roughened with diamond bur is higher than group treated with aluminum oxide and untreated group.The shear bond strength of delayed repair of amalgam is less than that of immediate repair, the surface produced by roughening the samples with a diamond bur will give best strength than the surface treated by aluminum oxide and untreated surface (smooth surface) and the same types of amalgam restorations used in amalgam repair gave better result than different type of amalgam.

Encoding differences affect the number and precision of own-race versus other-race faces stored in visual working memory

Other-race faces are discriminated and recognized less accurately than own-race faces. Despite a wealth of research characterizing this other-race effect (ORE), little is known about the nature of the representations of own-race versus other-race faces. This is because traditional measures of this ORE provide a binary measure of discrimination or recognition (correct/incorrect), failing to capture potential variation in the quality of face representations. We applied a novel continuous-response paradigm to independently measure the number of own-race and other-race face representations stored in visual working memory (VWM) and the precision with which they are stored. Participants reported target own-race or other-race faces on a circular face space that smoothly varied along the dimension of identity. Using probabilistic mixture modeling, we found that following ample encoding time, the ORE is attributable to differences in the probability of a face being maintained in VWM. Reducing encoding time, a manipulation that is more sensitive to encoding limitations, caused a loss of precision or an increase in variability of VWM for other-race but not own-race faces. These results suggest that the ORE is driven by the inefficiency with which other-race faces are rapidly encoded in VWM and provide novel insights about how perceptual experience influences the representation of own-race and other-race faces in VWM.

Upper-bound solutions for face stability of circular tunnels in undrained clays

The aim of this paper is to determine the critical supporting pressure on the circular face of an advancing tunnel in undrained clay in which undrained strength increases linearly with depth. Based on the kinematic approach of limit analysis, a continuous velocity field with a toric envelope is adopted to yield upper bounds of the face pressure for both collapse and blow-out. Combining with a closed-form expression describing the overall velocity field, an optimisation procedure is carried out to find the lowest upper-bound solutions. The calculated results are presented in terms of a dimensionless coefficient N (called the stability number) and then stability charts for use are produced. Alternatively, an approximation formula is given to estimate easily the collapse and blow-out pressure in practice.

Source wavelet and local wave propagation effects on the amplitude-variation-with-offset response of thin-layer models: A physical modeling study

In target layers with thicknesses below the vertical seismic resolution as thin layers, the tuning effect/interference between the wave propagation modes may increase the challenge of doing amplitude-variation-with-offset (AVO) analysis because it is difficult to recover the primary PP amplitudes embedded in the data by further seismic data processing. Thus, we have investigated the importance of the primary PP reflections, locally P-SV converted waves, and internal multiple reflections in the amplitude response of two thin-layer seismic physical models. One model consists of a thin water layer embedded between two nylon plates, and another model with a thin acrylic layer surrounded by water. Numerical modeling using the reflectivity method was applied to analyze each wave propagation mode and the source waveform role in the experimental data. Before the experimental reflection data acquisition, we characterized two source and receiver piezoelectric transducer (PET) pairs: one with a circular plane face and the other with a semispherical face. We measured the source wavelet, its dominant frequency, and the PETs’ directivity pattern. Semispherical PETs were chosen to acquire common midpoint reflection data. Thereafter, a processing workflow was applied to remove linear events interfering with the target reflections and to correct amplitudes due to transmission losses, source/receiver directivity, and geometric spreading effects. Finally, we investigated the thin-layer targets near incidence angle amplitude and the AVO response. The results showed that the interference between the primary PP reflections and the locally converted shear waves may considerably affect the observed amplitude response. The source wavelet bandwidth appeared as a second-order effect, and the internal multiple reflections were practically negligible. These results suggested that in real data sets, it is important to investigate the wave propagation modes and source wavelet role in the amplitudes observed, before deciding the AVO analysis/inversion workflow that should be adopted.